The long-term goal of this research is to determine how the adipocyte differentiation program is initiated and propagated, in particular, how key genes (specifically, the C/EBAalpha gene) that initiate and coordinate the program are transcriptionally activated or derepressed. This information may lead to new approaches for the prevention and/or reversal of obesity and its associated diseases including Type 2 diabetes. This approach should lead us to transcription factors that function earlier in the adipose developmental pathway. Three types of nuclear trans-acting factors have been identified which affect transcription mediated by the C/EBPalpha promoter: 1. CUP (C/EBPalpha Undifferentiated Protein, an apparent repressor of the C/EBPalpha gene). We have purified and partially sequenced CUP, and thereby identified AP-2Aalpha as a component of the CUP complex; 2. C/EBPalpha (which autoactivates transcription of its own gene) and other C/EBP family members; and 3. PPARgamma, which transactivates the C/EBPalpha gene. Our immediate goal is to determine how these factors regulate transcription of the C/EBPalpha gene and how they themselves are regulated. We have developed a new methodology whereby 3T3-F442A preadipocytes that harbor a transgene (e.g., promoter-reporter constructs or regulatory genes) can be implanted subcutaneously into athymic mice and develop into adipose tissue that can be analyzed for expression of the transgene and its function. The SPECIFIC AIMS are to determine: the role and mechanism(s) by which CUP/AP-2Aalpha (and possibly other components of the CUP repressor complex) regulates expression of the C/EBPalpha gene. the role(s) and mechanisms of action of other trans-acting factors (PPARgamma) and cis-regulatory elements (e.g., the Myc/Zif and Sp1 sites) that regulate the C/EBPalpha gene. how C/EBPalpha (and adipocyte genes it controls) is hormonally regulated in the differentiated adipocyte notably in insulin and cAMP.